Aug. 23, 2010 -- As the nation's largest egg recall continues, the FDA investigation is focusing on the huge egg farms in Iowa owned by Austin "Jack" DeCoster.

The CDC continues to receive new reports of salmonella illness from the strain of the bacteria implicated in the egg recall. Since May, there have been about 1,300 more confirmed cases of food poisoning with this strain than are usual for this time of year. The CDC estimates that for every reported case there are 30 to 38 unreported illnesses.

Some of these illnesses have been traced to eggs from two egg production facilities in Iowa. The parent company of both firms is Quality Eggs, one of several companies owned by DeCoster.

"We have more than 20 investigators on the ground in Iowa. We are evaluating potential causes of contamination at farms associated with the salmonella outbreak," FDA Commissioner Margaret Hamburg, MD, said today at a news teleconference.

The contamination could come from several sources. But Jeff Farrar, DVM, PhD, MPH, the FDA's associate commissioner for food protection, said that the Quality Eggs facilities received their chicks from a Minnesota firm certified to be free of salmonella.

If the chicks did not bring the salmonella with them, then they may have picked up salmonella at the Quality Eggs facility. The source could be contaminated feed -- and Farrar said Quality Egg is the source of the feed used on the farms to which the contaminated eggs were traced. Rodents and other pests, lax environmental controls, or other mishaps could also be sources of contamination.

To date, Farrar said, FDA investigators have not isolated salmonella from the suspected facilities. However, he noted that most of these tests are not yet complete. When they are -- perhaps later this week -- the FDA will issue the first of its official inspection reports.

The recalled eggs are packaged under a wide range of brand names. An updated list is on the FDA foodsafety.gov web site. But some of the eggs were distributed as loose eggs and may have been repackaged under different brand names. Farrar said it's likely that new "sub-recalls" will go out as investigators learn of these repackaged brands.

So far, eggs have been recalled in 22 states.

Christopher R. Braden, MD, acting director of the CDC's division of food-borne diseases, said some states have reported hundreds of cases.

Since the recall began, the CDC has not identified any new clusters of salmonella cases -- that is, people who got sick after eating at the same restaurant or attending the same event.

"Some of these illnesses could have sources other than eggs. The issue is determining who is part of the outbreak and who is not. That can be difficult," Braden said.